Technical Field
The present disclosure relates to a substrate, and more particularly, to a pixel array substrate of a display panel.
Description of Related Art
Liquid crystal display (LCD) panels have become the mainstream display products because of advantages such as low radiation, low power consumption and compact size. A variety of techniques in the LCD panels are developed corresponding to different needs. Among which, Vertical Alignment (VA) of the wide viewing angle display technology has wider viewing angle than that of Twisted Nematic (TN), fast responding, and high contrast ratio, thus has been widely applied in a LCD panel.
However, the VA LCD panel is known for its color washout issue. To solve the issue, the pixel area of the pixel array substrate of current VA LCD panels is divided into two parts. As illustrated in FIG. 1 and FIG. 2, FIG. 1 is a top-view of the conventional pixel, and FIG. 2 is the equivalent circuit diagram of the pixel illustrated in FIG. 1. Referring to FIG. 1 and FIG. 2, pixel 100 includes a first pixel electrode 102, a second pixel electrode 104, a first connecting line 106, and a second connecting line 108. The first electrode 102 is electrically connected to its corresponding data line DL1 and scan line SL1 through the first connecting line 106 and the a switch T1; The second pixel electrode 104 is also electrically connected to its corresponding data line DL1 and scan line SL1 through the second connecting line 108 and a switch T2. In addition, pixel 100 also includes a switch T3, storage capacitors CST1, CST2, common electrode VCOM, liquid crystal capacitors CLC1, CLC2, and charge-sharing capacitor Cs (CCSA and CCSB). Switches T1, T2, and T3 are thin-film transistors (TFT), for example. Liquid crystal capacitors CLC1, CLC2 respectively represent the capacitances which are generated between pixel electrode (the first pixel electrode 102 and the second pixel electrode 104) and the electrode(s) applied with VCOM voltage on the opposite substrate of the LCD panel (not illustrated in FIG. 1 and FIG. 2). CST1 and CST2 respectively represent the capacitances which are generated between common electrode applied with VCOM voltage and each pixel electrode (the first pixel electrode 102 and the second pixel electrode 104) of the pixel array substrate of the LCD panel. Charge-sharing capacitor Cs is an extension from the switch T3, charge-sharing capacitor Cs forms capacitors with other conductive layers, for example, CCSA is the capacitor formed between the first pixel electrode 102 and Cs, and CCSB is the capacitor formed between the common electrode VCOM and Cs.
As to the main display area which corresponds to the first pixel electrode 102, the switch T1 is electrically connected between data line DL1 and the first pixel electrode 102. The switch T1 is also electrically connected to scan line SL1, and a signal passing through scan line SL1 controls the switch T1 to turn on/off. The storage capacitor CST1 is electrically connected between the first pixel electrode 102 and the common electrode VCOM. When the switch T1 turns on, a data signal of data line DL1 is transmitted through the switch T1 to the first electrode 102, so that the storage capacitor CST1, is charged to have corresponding voltage.
As to the secondary display area which is corresponding to the second pixel electrode 104, the switch T2 is electrically connected between data line DL1 and the second pixel electrode 104. The switch T2 is also electrically connected to scan line SL1, a signal passing through scan line SL1 controls the switch T2 to turn on/off. The storage capacitor CST2 is electrically connected between the second pixel electrode 104 and the common electrode VCOM. When the switch T2 turns on, a data signal of data line DL1 is transmitted through the switch T2 to the second electrode 104, so that the storage capacitor CST2 is charged to have corresponding voltage. To solve the issue of color washout of the LCD panel, charge sharing is performed. After the first pixel electrode 102 and the second pixel electrode 104 are charged by the signal from scan line SL1, in next time sequence, the switch T3 turns on by the signal inputted from scan line T3, so as a part of the voltage of the second pixel electrode 104 is shared to the capacitor CCSB and the other part of the voltage of the second pixel electrode 104 is shared to the capacitor CCSA through the switch T3. It results in charge sharing between the first pixel electrode 102 and the second pixel electrode 104 by the charge-sharing capacitor Cs, the voltage of the first pixel electrode 102 increases and that of the second pixel electrode 104 decreases. Therefore, the voltages of the first pixel electrode 102 and the second pixel electrode 104 are different. It causes the tilting angle of liquid crystals corresponding to the first pixel electrode 102 and the second pixel electrode 104 are different within the same pixel 100, so as the brightness within the same pixel 100 can be optimized since the transmittance within the same pixel 100 can be different, thus the issue of color washout can be solved.
However, continually referring FIG. 1 and FIG. 2, as illustrated in dot lines area of FIG. 1, in the path of the second connecting line 108 connecting to the second pixel electrode 104, part of the path is underpass the first pixel electrode 102. This overlapping structure of the second connecting line 108 and the first pixel electrode 102 in vertical direction will generate an extra coupling capacitance Cx as illustrated in dot lines area of FIG. 2. When the coupling capacitance Cx is generated between the first pixel electrode 102 and the second pixel electrode 104, charge sharing will be weaken. Thus the effects of the voltage increase of the first pixel electrode 102 and the voltage decrease of the second pixel electrode 104 are diminished. Therefore, to increase the voltage difference between the first pixel electrode 102 and the second pixel electrode 104 becomes difficult. In order to maintain the voltage difference between the first pixel electrode 102 and the second pixel electrode 104 to solve the color washout issue, further increase the capacitance of the charge-sharing capacitor Cs to release more electric charge from the second pixel electrode 104 and lower the voltage of the second pixel electrode 104 is generally performed. However, the efficiency of the LCD panel is decreased to maintain the voltage difference between the first pixel electrode 102 and the second pixel electrode 104 in this way.